Our puppy is 4 months old and is very active, the thing that concerns me is that he likes to jump. I have heard so many things saying that they will be injured by jumping that I am panicked. (he is not super heavy maybe 55lbs) He is not jumping off of things but he like to run and jump for his rope, or falling leaves or tree limbs. I wonder is this ok, and if not how do you stop them? We love him so much but we are on pins and needles because we are afraid that we are over exercising him or playing too much with him. Everything you read seems to say they are fragile until the are 18 months. Any advice would be truly appreciated.